1. Technical Field
The present invention relates to a liquid ejecting apparatus including a liquid ejecting head for ejecting a liquid from a nozzle opening and a method of driving a liquid ejecting head.
2. Related Art
An ink jet recording apparatus such as an ink jet printer or plotter includes an ink jet recording head capable of discharging ink stored in an ink storage unit, such as an ink cartridge or an ink tank, as an ink droplet.
The ink jet recording head includes a pressure generating chamber which communicates with a nozzle opening, a reservoir which is a common liquid chamber that communicates with a plurality of pressure generating chambers, and a pressure generating unit which generates a pressure variation within the pressure generating chamber to discharge a droplet from the nozzle opening. The pressure generating unit installed in the ink jet recording head may include, for example, a longitudinal vibration type piezoelectric device, a bending deformation type piezoelectric device, or a device using an electrostatic force, or a heat generating device, or the like.
Some problems occur when the ink droplet is discharged by the ink jet recording head. For example, a tail of the discharged ink droplet may be lengthened, or a very small amount of secondary ink droplets may be discharged. In this case, it is impossible to perform a high speed printing or a high frequency discharging in which a plurality of ink droplets are discharged with a rapid timing.
Therefore, JP-A-2-184449, JP-A-2006-306076, and Japanese Patent No. 3275965 discloses a contraction element for discharging an ink droplet by contracting the volume of the pressure generating chamber using a driving signal supplied to the pressure generating unit such as a piezoelectric device and an inflation element for severing an ink pole by inflating the pressure generating chamber.
However, as high-speed printing is more and more in demand, it is necessary to further shorten the tail of the ink droplet. Therefore, a method of abruptly changing the voltage by increasing the driving voltage of the inflation element to sever the ink pole, and reducing the time for applying the voltage has been proposed. However, if the voltage is abruptly changed, vibration of the meniscus of the ink within the nozzle opening after discharging the ink droplet also increases so that a secondary ink droplet may be discharged or the discharge of a subsequent ink droplet may be adversely affected.
Such a problem cannot be addressed by the patent documents described above. In addition, such a problem becomes significant when ink having a high viscosity is discharged.
Such a problem also occurs in a liquid ejecting apparatus which ejects a liquid other than ink, as well as the ink jet recording apparatus.